Apparatus and process for pressing detergents



June 25, 1963 1. A. DowNlE ETAI. 3,094,758

APPARATUS AND PROCESS FOR PRESSING DETERGENTS Filed Aug. 7, 1959 3 Sheets-Sheet 1 lll/lll//l/l//l/l/ll/ IN1/ENS JOHNARTHUR DOWN/E BY W/LL/AMBOYD @wf/QM@ ATTORNEY APPARATUS AND PROCESS FOR PRESSING DETERGENTS Filed Aug. '7, 1959 June 25, 1963 1. A. DowNlE ETAL 3 Sheets-Sheet 2 JNVENTORS JOHN ARTHUR Do w/v/f BY WILL/AM BOYD June 25, 1963 J. A. DowNlE ETAL APPARATUS AND PROCESS FOR PRESSING DETERGENTS 3" Sheets-Sheet 3 Filed Aug. '7, 1959 w Z .b I lrl, afW W0 w INVENToRs JOHN ARTHUR D0 wN/E BY W/LL/AM BOYD tas Filed Aug. 7, 1959, Ser. No. 832,279 Claims priority, application Canada Aug. 12, 1958 Claims. (Cl. 25-7) The present invention relates to a new apparatus for pressing detergents into bars or cakes. More particularly, the invention is of an apparatus capable of manufacturing detergent cakes at high speed, which includes a pair of opposed companion die members of soft, ilexible, resilient, polymeric synthetic organic plastic, each having a rigid member embedded therein. Within the invention are included processes `for the manufact-ure of these die members as well as processes of pressing detergents with such soft plastic dies.

Detergents pressed with soft plastic die members contain fewer die marks than those pressed by metal dies. Detergent presses operating with plastic `dies require less lubrication of the detergent to promote die release, do not discolor the detergent -being pressed and may be run for comparatively long times without necessity of shutdown for cleaning of dies. Although some soft plastics may tend to distort excessively during the pressing operation, especially at the die working surface, the dies of structure here described and in the appended claims do not distort to an objectionable extent. Designs on the faces of detergents pressed with them are clear and sharp, as desired.

In accordance with the present invention there is provided an apparatus for pressing `detergent materials into cake form at high speed -which comprises a die box, a pair of relatively movable opposed companion die members of soft, flexible, resilient, polymeric synthetic organic plastic, smaller than the die box cavity to allow a clearance between dies and `die box as the dies enter the die box cavity and having pressing surfaces, the peripheral edge portions of the pressing surfaces of the dies being capable 0f expanding after contact Iwith the detergent to be pressed due to the pressure exertedon the dies by the detergent as it resists compression, the dies each having embedded therein a comparatively rigid member so located that a pressing force applied to the die will cause it to press detergent material without objectionable distortion of the pressing face of the die, but will allow the peripheral edge portion thereof to expand to the die box under pressure of the detergent on the pressing surface and thereby eliminate the clearance between die and die box at the pressing surface and prevent ilashing of the detergent, and pressing means operatively connected with the die and capable of rapidly and repeatedly imparting a pressing force to it. Also Within the invention is a method of making such a detergent press die member of soft, flexible, resilient, polymeric synthetic organic plastic, which comprises filling with such a plastic a walled, bottomed mold cavity having substantially parallel vertical walls and a bottom portion with an upper surface shaped and figured like the desired face of a detergent bar to be pressed by the die; maintaining the temperature of the plastic at a point at which it is uid; applying pressure to the plastic, forcing it against the bottom and sides of the mold; holding a rigid member in the mold in such position as to be in substantial contact with the molten plastic; cooling the plastic until it is solidied while holding it under pressure; and removing the molded detergent pressing die from the mold with the rigid member afxed thereto.

arent 0 ice The structure, function and advantages of the present invention will be apparent from reference to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. l is a side elevation of a lettered soft plastic die containing a rigid plate member parallel to the die Working surface thereof;

FIG. 2 is a horizontal section of the die of FIG. 1;

FIG. 3 is a side elevation of another soft plastic die containing a modied rigid member;

FIG. 4 is a horizontal section of the die of FIG. 3;

FIG. 5 is a central horizontal sect-ion of a soft plastic die containing a rigid member, illustrating the attachment thereto of fastening members and pressing means;

FIG. 6 is a central horizontal section of a die box having a cavity, with opposed soft plastic dies at the entrance thereof;

FIG. 7 is a central horizontal section of the die box and dies of FIG. 6 with the dies in closed position in pressing contact with detergent being shaped into cake form, the soft edges of the dies making contact with the die box to prevent flashing of the detergent during pressme;

FIG. 8 is a perspective view, with some parts removed for clarity of exposition, of high speed detergent pressing apparatus embodying features of this invention;

FIG. 9 is a plan view of a mold yfor making the invented plastic -dies showing the path of heating fluid or coolant;

FIG. l0 is an elevation of the mold of FIG. 9;

FIG. 1l is a vertical sectional view of the mold including pressing apparatus for molding the invented soft plastic detergent pressing die.

Numeral 30 designates a soft plastic die member having a raised thin edge 32 which is sufficiently flexible and resilient to expand outwardly when subjected to pressing forces. Die 30 has inverted lettering 34 appearing on the face for stamping detergent cakes to be pressed with brand identification or other descriptive material. Similarly, patterns and designs may be molded or impressed into the die -face so that lthe detergent cake may be attractively decorated. In the interior of soap die 3l) near to the die working surface 36 is embedded a rigid member 38 which is of sufficient size and near enough to working surface 36 containing design, figures or lettering 34 to decrease or inhibit distortion of said figures during detergent pressing operations. the fastening of the die to the pressing means, allowing a bolted attachment which would not be possible with all soft plastics because the plastic threads or other holding device would yield or fail. The rigid member is preferably of metal, such as steel or brass, but other materials of suicient iirmness may also be employed. As illustrated the rigid member is of relatively flat plate shape. To promote firm fastening to or embedding in the die the surface of the plate may be scored, perforated or grooved. The distance between working surface 36 and member 38 will be variable to some extent, depending on the plastic employed, but wil-l usually be between 1/16 and 3A of an inch. This dimension should be enough to allow the plastic near the edge of the rigid member to lbe resilient enough to absorb the shocks of pressing without failing before a sufcient number of cakes has been pressed. In FIGS. 1 and 2 rigid member 34 is shown having a pair of tapped holes 40 into which fastening bolts or studs may be screwed through bores 41 to attach the die to a pressing member.

In FIGS. 3 and 4 there is illustrated another embodiment of av suficiently -rigid die 43 for pressing detergents which contains a single perforation 42 in the rigid `member 44, through which perforation the plastic above and This element facilitates' below the rigid member is communicated. This construction is achieved Iby molding the perforated rigid member into the die during its manufacture. The rigid plate may also be inserted in a hollow in the die structure and the die portions may then be cemented or fused closed. The plate may be firmly fastened to the die by any suitable adhesive or other bonding means. The plastic die as shown in FIGS. 3 and 4 contains a band of thin sheet material 46, usually metallic, fastened about the exterior of member 44. At the top of this band, which is more 4rigid than the soft plastic of the die, a thin edge 48 projects above the leading surface 50 of the rigid member and towards the leading portion 52 of the thin raised edge of the die member. This thin projecting edge serves to stiffen to a desired degree the soft die material. Such a structure allows the use of plastics which would otherwise be too soft (even with an internal rigid member) and the raised thin edges of which would be too easily distorted by forces attendant the pressing of detergents. The degree of extension of the projecting band beyond the leading face of the rigid member will regulate the deilection of the plastic thin edge 52 during pressing. It should be noted that it is important to the present invention that the thin raised edge of the die should be expandable to the die box and in many instances the soft plastics to be used will not require any special strengthen- Iing of the expandable die edge. Nevertheless, should such deflection be considered too great, it may be regulated by utilizing the described structure.

'In FIG. 5 there is shown a joinder of the die to pressing means by fastening members. The soft plastic die, as illustrated, is the same as that shown in FIGS. l and 2 except for an illustration of undercutting the leading edges of the dies at 7S by reducing the die dimensions a short distance below the leading edge. This modification avoids any need for machining side walls to avoid an increase in thickness of the sides near the rigid member, resulting from lesser shrinkage of the plastic there after molding. A pair of socket head screws 76 is screwed into the threaded portions 40 of the rigid member 38. These fastening members are removable from the detergent pressing die but in other contemplated designs studs may be permanently molded therein with the rigid member. The screws hold pressing means 80 to the plastic die by joinder to the rigid member 38. In the embodiment illustrated the inset socket head screws 76 are threaded into the rigid member but in similar apparatuses other methods of attachment may be employed. In some eases it may be desired to have the screws 76 longer so that the backing plate 80' does not make the actual contact with the plastic of the die. In such case the screws 76 should be firmly positioned and should -be made of a very strong material not subject to any objectionable sideward bending when contact is made with the deter-gent during pressing. This is so lbecause in such` a structure the plastic contact with the backing plate is absent and its frictional holding action on the die is lost. Studs 78, washers 84 and nuts 82 are used to fasten the pressing means or back-ing plate 80 to a ram or other element of .the pressing machine.

In FIG 6 is shown a pair of opposed die members entering a cavity of a conventional die box spider. The clearance 90 between dies 30 and die box 91 is exaggerated in the drawing so that, in conjunction with FIG. 7, the action of the ilexible raised edge portion of .the soft plastic may be better seen. This clearance should usually be between 0.001 and 0.050 inch, depending lon the particular plastic and die design employed, (meaning that the die -is 0.00'12-01 inch shorter and narrower than the die box internal measurements). With polymers of lower alkylenes it is preferable to maintain the clearance between 0.00l and 0.006 inch and best results with polyethylene are obtained in the comparatively narrow range of 0.003 to 0.005 inch, 0.004 being usually considered to be best A cut length of plodder bar or blank 92 of soap,

i symthetic detergent or mixture thereof, is shown in the die box cavity lbetween the opposed dies. It will be noted that the raised thin edges 32 of the dies and even the leading surfaces 94 of the rigid members 38 are within the confines of the die box 91 before a pressing force or substantial part thereof is applied to the soap blank by the plastic die working surface 36. Thus, there will be no substantial expansion of the raised edges 32 of the dies until after they are within the die box and cutting and tearing of the die leading edges caused by striking the die box on entry will be avoided. In FIG. 7 there is shown the expansion of the leading edges 32 as the opposed dies 30 force the detergent blank into desired iinished cake shape 93. It will be seen that in a preferred operation only the leading raised edge portions of the dies are brought into contact with the die box Wall 96, leaving clearance 90 between dies and die box. Such minimum contact apparently helps to allow more rapid breaking of lthe vacuum Ibetween the die working surfaces 36 and the pressed detergent because air can enter the die box more easily. It is also possible that the tendency of the plastic to resume its original straight-sided shape may be contributory to sliding movement of the raised edge portions 32 of the dies along the curvatures 100 of the detergent cake as the dies 30 are withdrawn, thereby facilitating the entry of a-ir between the raised edges of the die and the detergent. Minimizing contact between die box and sides of the `die also decreases wear of sides 98 thereof and prevents roughening or tearing of the sides which might lead to serious pressing problems. It also lowers the drag of die box on the die which drag otherwise might lbe great enough to seriously decrease the applied pressing force.

` scribed concurrently. Detergent blanks 92 are fed into guide box 108 by -belt 120. Vertical pusher 118 raises one of the detergent blanks to the top of the guide box fwhere it is held by the lateral pressure of the guide box walls 110. Bottom pusher 116 rnoves the blank into the port of the guide box and against stops 112 where it is supported and held by shoulder 1214. At the next upward stroke of vertical pusher 118 a second blank of detergent is raised to the top of the guide box and the next forward stroke of pusher 116 moves the second blank into the port, thereby forcing the Viirst blank from the guide box into a receiving cavity 106 at the lowermost portion of cruciform spider 102. The -spider is then rotated 90, usually at a rate between 10 and 40 revolutions per minute, and the detergent blank is in position for pressing between opposed soft plastic dies 30. Die members 30 are of almost the same cross-section as the die box cavity j106 with provision for slight clearance. These dies are adapted for horizontal reciprocation into each of the cavities successively -upon registration of the die box with the dies. Pressing means or backing plates are affixed to the die members by screws 76. These .pressing means are likewise removably connected in any suitable manner with drive means or ram 124 for reciprocating the dies. In the illustrated apparatus, to simplify the drawing and disclosure, no trimmer for the soap blanks has been shown. Normally, such a device will be employed to shape the blanks before they are inserted in the die box. It is evident that other modifications of the apparatus are permissible in which the blanks are positioned in the die box by other suitable feeding structure.

The opposed dies 30 are brought forcibly together With sucient pressure, eg., about 50"-2,000 pounds per square inch, to press the detergent blank into a cake of shape defined bythe dies and die box. The die boxes are usually shaped cavities in the spider, which is normally of metal or hard plastic, but they may also be equipped with hard or soft plastic liners 1014, as may be best suited for contact with a particular detergent being processed. As the blank is pressed into shape the compressing force on the detergent forces the raised thin edges 32 of the soft plastic dies outwardly against the wall of the die box cavity. This action causes the die itself to serve somewhat as a valve and prevent dashing of the detergent past it and through the clearance space. The absence of ashed or extruded detergent in this space helps avoid marking of subsequently pressed cakes with the ilashings from previous pressings and decreases the necessity for periodic shutdowns of the press Vfor cleaning of dies.

Horizontal reciprocating top pusher 126 is located near the spider in horizontal alignment with a receiving cavity at the uppermost posi-tion of the spider. Take-oli belt 132 is located below the uppermost cavity on the side lof the spider away from the pusher and carries pressed detergent cakes 93, of which one -is shown after ejection by pusher 126 yto a wrapping station or other machine or operation.

'In FIGS. 9-11 ta mold 151 for the manufacture of the novel detergent pressing dies is shown in detail. The mold body is constructed of a bottom 152 joined by -machine screws 154 to substantially parallel vertical walls 156. To the bottom or base plate -there is @fastened by machine screws 158 Within the enclosure of base plate and walls another bottom 160 shaped and gured like the desired face of a detergent bar to be pressed by a molded die. A piston 162 is capable of :applying a high pressure to plastic within the mold. The piston is attached to pressing means by any suitable connection, such as studs 163 and plate 164. In the illustration given, between said pressing means, not shown, and the piston rigid plate member 164 is drilled and tapped for studs 166, the purpose of which will be explained. The tap holes `165 in plate 164 register with drill holes 168 through piston 162 in which are frictionally fitted rods 170 threaded at the lower ends into rigid member 172. By rotation of studs 166 rigid member 172 may be lowered into the mold so as to be as near the bottom 160 as is necessary or desirable to limit distortion of the molded die working tace member, either while cooling after molding or during pressing of detergent, and to provide a satisfactory means of `fastening the die to the pressing apparatus.

The, sides of the mold contain inter-connected channels 174 for the passage of heating or cooling iluid to melt or solidify the soft plastic. As will be seen from a study of FIGS. 9 4and l0 the heat trans-fer lluid enters the mold at 176 and exits at 178, pursuing a path 'as indicated by .the arrows (the arrows in FIG. 9 yshowing flow at the lowermost or" the three levels). The channels for passage of heat transfer iluid are made by boring lholes parallel to each side `of the mold `at three 4levels and by connecting these levels by means of holes `drilled from 180 to 182 and from 184 to .186. All `drilled and bored holes communicating with the exterior of the mold are plugged, as shown by shaded portions, except at the inlet and outlet. 'It is seen that the liquid heat transfer medium enters the mold Iat the inlet hole at the right rear corner of the bottom level. lIt divides into two streams ilowing toward the diagonally opposite corner lof the mold where it ows upward .toward point 182, whence it pursues two paths on the :middle level toward point 184, from which it rises to the top level, divides and exits from outlet 178. -By following a tontuous path such as that described the heat transfer medium rapidly and evenly alters the temperature of the mold. It will be evident that other methods of heating and cooling the 6 mold and the plastic therein may also `be found adequate -in the present molding process.

'In operation the mol-ding of the present detergent pressing dies is trouble free and economical. In a typical process the beads of plastic resin, generally a thermo plastic because of the ease of melting and soliditication of these materials, are heated until they become liquid 4after which the plastic is poured into the lmold. Alternatively, the particles of resin may be placed in the mold and then heated until ll-uid. The piston having attach-ed force-transmitting members 17 il and rigid member 172 is lowered into the mold and a compress-ive force is applied to it by the pressing means. In this compression molding operation the piston or plunger should be able to withstand high pressures on the order of 500-2,500

pounds per square inch. In the molding .of polyethylene it has been found that a pressure of approximately 1,400 pounds per ysquare inch is best for manufacture of an undistorted die. After the piston has :applied its full pressure to the molten plastic and has traveled downwardly as far as it can go studs 166 may be turned to lower the tightly iitted rods 170 and thereby move the rigid member 172 to the predetermined correct distance above the mold bottom. As illustrated in FIG. ll no means has been provided for adjusting upward the height of rigid member 172 because this is not usually necessary. However, it is evident that, should such adjustment be considered advantageous, studs 166 Iand rods 170 can be so connected as to allow vertical movement ot the rigid member 172 in either directiony while molding- Aft-er the piston and rigid member have been positioned correctly coolant is allowed to ow through the mold walls. Generally the mold and piston are constructed of heat conductive material to promote rapid solidiication of the plastic. Dur-ing lthe entire coolin-g cycle it is best to maintain pressure on the plastic. This, in conjunction with the presence of the rigid internal member helps to maintain the dimensional stability of the molded article. It has been found that the molded die will `often be widest near the rigid internal member, due Ito less shrinkage at that position. Thus, the dimensions of the die are controllable to an extent by relocation of the rigid member in the soft plastic. After the molded die has been cooled to a point below which shrinkage distortion is negligible, usuallyl to near room temperature, the base plate is removed and the molded die With piston 162, and rod 170 attached and bottom 160 adhering is removed from the mold. The base plate may be taken ofi after removal of machine screws 154 and 158. The piston may be released by -tightening studs 166. Should bottom remain held .to a plastic die after it has been taken out of the mold release may often be effected by striking the bottom a sharp blow with a rubber hammer in 1a direction. parallel to its major surface.

The molded soft plastic die may be put into operation with threadedy rods still held fast or, if desired, these may be removed and other force-transmitting members can be attached to the die. In a particular preferred molding operation the pressing means 164 and the piston 170 are bored so that threaded rods or screws 76, as held in the nished die, will be registered with holding means in the detergent pressing apparatus. Thus, the molded die will be automatically positioned in the pressing apparatus die box with the proper clearance on all sides. It will often require no machining or fitting to the detergent press and may be put in operation without any further processing except for the removal of mold marks, if necessary.

In the preceding paragraphs a method of compression molding of soft plastic soap dies has been described. Although compression molded dies, as a rule, are of greater dimensional stability it is also possible to make properly designed soap dies by injection molding. In such cases the rigid member can be attached to the soft plastic during the molding operation, and sometimes may be joined to a separately molded plastic portion after molding, preferably by cementing, but bolting may also be employed.

Although dies made of harder plastics, of structure like that described in this specication, may be used in pressing soaps and detergents, there is a real advantage in the use of dies of the softer materials, because they are even more suitable for pressing detergents. The softer the plastic the more easily the raised thin edge of the die will be expandable to the die `wall. Often the softer material will show less wear in operation than will harder plastics. With the use of the softer plastics greater clearances between die and die box may be obtained because the die edge is capable of greater expansion. Increased clearances allow easy expulsion of air as the die closes on the detergent blank, obviating the cushioning effect of entrapped air and decreasing the pressing time needed to obtain a perfectly pressed cake. They also help prevent contact of the die edge with the die box, when entering, even if they are not perfectly aligned.

Among the plastics that may be employed the most preferred are the polymers of lower alkylenes, e.g., polyethylene, polypropylene, mixed polymers of ethylene and propylene. It has been found that these lower alkylene polymers possess exceptionally good release characteristics, i.e., soaps and synthetic detergents are non-adhering to these plastics. Among the polyalkylenes those Soft plastics known as polythene or polyethylene are preferred. As examples of suitable polythene resins from which the dies may be made may be mentioned types 204-E-07, 220G and 1200H produced by Canadian Industries Ltd.; such suitable materials have tensile strengths at yield of about 1,500 pounds per square inch, melt indexes between about 0.2 and 50 grams/ l0 min. and densities at 25 C. between about 0.915 and 0.910 grams/ml. These plastics, the polyethylenes, are generally described by their density and melt indexes. As the density increases the stiffness increases and the flex life decreases. With the same molecular weight distribution (weight average molecular weight/ number average molecular weight) and constant density a higher melt index indicates a decreased tensile strength. If only molecular weight distribution is increased tensile strength also increases. Although the characteristics of density, melt index and molecular Weight distribution are usually intended to aid the molder of plastics they are also of assistance in enabling one utilizing these materials to determine which plastics are most likely to be acceptable for his particular purpose. In experimentation done with various polyethylenes it has been found that soaps can be pressed successfully with polyethylene dies made from Canadian Industries Ltd., ZZOG, 204-E-07 and 12001-1 resins but dies of 01500A resin were not considered to be satisfactory. It is possible that 01500A resin may be used in some applications with rigid member closer to the die working surface or extending farther toward the raised thin edge, thereby better controlling distortion. Of the resins which gave good results type 220G, which has a melt index of 2.0 and a density of 0.919 was best. Included within the types of polyethylene that may be used for soap pressing dies is the more recently developed material of higher density, resins of density of 0.94 and higher being acceptable. The Alathons of E. I. du Pont de Nemours & Co. Inc. are also useful polyethylene resins from which soft plastic dies can be made. These products cover a comparatively wide range of polyethylenes those from Alathon 3 to Alathon 37 having melt indexes between 0.25 and 20, densities from 0.914 to 0.930 and molecular weight distributions from very narrow, less` than 5, to 40. Weight average molecular weights within the range of 25,000-l,000,000 are most common.

Although soft polyethylenes and polyalkylene plastics are the preferred materials of the present soap pressing dies it is also possible to employ other soft plastics, such as polyvinyl chloride, polyvinyl-vinylidene chlorides, polymers obtained by interaction of bi-functional alkyl or aryl silanes with each other and with glycols and diamines, e.g., polyphenolsiloxane `(silicones), polytetrailuoroalkylene, as well as thiokol-modied and polyamide-modiiied epoxies. Harder plastics, such as polystyrene, polycarbonates, cellulose acetate, polymethylmethacrylate (Lucite), dirnethylolrnelamine, condensation products of dimethylol phenol with excess formaldehyde, copolymer amides of adipic acid with sebacic acid and hexamethyl enediamine, halogenated or chlorinated polyethers, Vand many others may also be useful, providing that the polymer chains are of insuicient length to actually make these into hard plastics or the plastics are so modified with plasticizers or by other means so as to result in soft products. Limitations on the type of soft plastic that may be employed are those which will be evident to one skilled in the detergent art. In the die structure employed it must be of suiiicient strength to press out the detergent and yet should be soft enough to expand readily to ill the die box. It must not react chemically with the material being pressed, nor with lubricating solutions that are employed in the pressing of detergents. The plastic must be resistant to distortion due to repeated impact, must not fatigue, and should not be too readily abraded by sliding contact of other surfaces. The term soft plastics should be interpreted to include those materials which are polymers of fairly high molecular Weight, characterized by having a modulus of elasticity less than 5 l04 pounds per square inch, a compressive strength below 10,000 pounds per square inch and a llexural strength under 8,000 pounds per square inch. Usually such soft plastics will have a modulus of elasticity below '5.5 104 pounds per square inch, a compressive strength below 8,000 pounds per square inch and a ilexural strength below 7,000 pounds per square inch. Where the standard tests are not applicable because the plastic is too soft these characteristics are considered as less than the limits given. In some instances either one or two of these characteristics may be numerically above the ranges given but the other modulus will be low enough to compensate for these and the product will still be considered as soft. Thus, if one of the above properties is below the limits given, the product may often be considered as within the scope of the materials suitable for use as the present plastic dies.

In operation in a detergent pressing apparatus the soft plastic dies of this invention may be used in much the same manner as that in which the prior art metallic and rigid dies were employed. Being molded to shape and of flexible edge structure, machining and fitting of the dies will usually be unnecessary and they may be readily affixed to the detergent press in pre-registered relationship with the die box if that is desired. After axation of the die to the pressing means a check run will speedily show whether the particular soft plastic can completely press out the detergent blank. If the lettering and designs on the detergent cake are not sharply dened it may be desirable to use a slightly harder, less yielding material for the die. Alternatively, it is often possible to cast another die, relocating the rigid member in the die to make the die firmer. It will often be found that utilizing a plodder nozzle or trimmer of shape more like that of the finished cake will facilitate pressing the detergent, as will increasing the moisture content of the soap or synthetic detergent to soften it.

Because polyethylene is non-adherent to soaps and synthetic detergent materials, a reduced amount of pressing solution should be employed, if such lubricant is used at all. The pressed bars will normally be discharged from the die box with a surface sheen or gloss much higher than that obtained when metal dies are used. The soap or detergent will not tend to adhere to the dies and consequently the machine need not be stopped as often for cleaning to avoid die marks. In some instances these dies have been run as long as an hour or two processing soap at the rate of about 120 cakes per minute without shutdown for cleaning.

The present soft plastic dies are long-lived when treated carefully. In test runs the described dies have been employed as long as five weeks, producing soap at the rate of 120 cakes per minute over a full eight-hour period, iive days a week. At the end of that time the dies finally showed sorne signs of wear and were discarded, to be replaced by a new set. The inexpensiveness of the present soft plastic dies dictates their periodic replacement to assure that the detergent made has the best impression. It is more economical to replace these plastic dies than to reiinish metal dies that have become worn.

In this specification at times the words upper, lower, top and bottom were used in describing the apparatus employed. It should be understood that these terms are not to be construed strictly because they were employed to simplify the description and to show the relative positions of various parts.

What is claimed is:

l. Apparatus for pressing detergent materials into cake form at high speed which comprises a die box, a pair of relatively movable opposed companion die members of soft, flexible, resilient, polymeric synthetic organic plastic, smaller than the die box cavity to allow a clearance between dies and die box as the dies enter the die box cavity and having pressing surfaces, the peripheral edge portions of the pressing surfaces of the dies being capable of expanding after contact with the detergent to be pressed due to the pressure exerted on the dies by the detergent as it resists compression, the dies each having embedded therein a rigid member so located with respect to the pressing face of it that a pressing force applied to the die will cause the die to press detergent material without objectionable distortion of the pressing face, but will allow the peripheral edge portion of the die to expand to the die box under pressure of the detergent on the pressing surface and thereby eliminate the clearance between die and die box at the pressing surface and prevent ashing of the detergent, and pressing means operatively connected with the dies and capable of rapidly and repeatedly imparting a pressing force to them.

2. Apparatus for pressing detergent materials into cake form at high speed which comprises a die box, a pair of relatively movable, opposed, companion die members of soft, llexible, resilient, molded polymeric synthetic organic plastic, smaller than the die box cavity to allow a clearance between dies and die box as the dies enter the die box cavity and having on at least one of the dies a pressing surface containing raised figures, both dies having a raised peripheral edge portion capable of expanding outwardly after contact with the detergent to be pressed due to pressure exerted on the die by the detergent as it resists compression, the dies each having moldedr and embedded therein a substantially at rigid member of suflicient size and near enough to the pressing surface so that an applied pressing force will cause the die to press the detergent material without objectionable distortion of the pressing face of the die and ligures thereon, but will allow the raised Iperipheral edge portion thereof to expand to the die box under pressure of the detergent on the pressing surface and thereby eliminate the clearance between die and tdie box at the pressing surface and prevent ilashing of the detergent, and pressing means operatively connected with the rigid members and capable yof rapidly and repeatedly imparting a pressing force to the dies.

3. Apparatus for pressing detergent materials into cake form at -high speed which comprises a die box, a pair of relatively movable, opposed companion dies of soft, ilexible, resilient, compression molded polymeric synthetic organic plastic, smaller than the die box cavity to allow a clearance between dies and die box as the dies enter the die box cavity and having on at least one of the dies a pressing surface containing raised gures, both dies having raised peripheral thin edge portions, ycapable of expanding outwardly after contact with the detergent to be pressed due to the pressure exerted on the dies by the detergent as it resists compression, the dies each having embedded therein a rigid member molded into the die, said member being substantially at a right angle to the path of the die and substantially parallel to the die pressing surface and having a substantial portion of the leading surface thereof substantially parallel to the pressing surface and of sucient size and near enough =to the pressing surface so lthat an applied pressing force will cause the die to press the detergent material Without distortion of 'the pressing face Iof the die, but will allow the peripheral edge portion thereof to expand so far as the internal Wall of the die box under pressure of detergent applied to the pressing surface and thereby eliminate the die-to-die box clearance at the pressing surface and prevent flashing of the detergent, the die members also having side and end walls of lesser cross-section than the sur-face thereof, a pair yof reciprocating members capable of exerting pressing @forces on the dies through the pressing -means to which they are fastened, and fastening means for holding the dies to the pressing members by joinder to the ernbed-ded rigid members thereof.

4. An apparatus according to claim l in which the die members are of molded poly-lower alkylene plastic.

5. An apparatus according to eclaim 4 in which the die lmembers are of molded polyethylene.

References Cited in the file of this patent UNITED STATES PATENTS 1,218,568 Kennington Mar. 6, 1917 1,218,596 Conklin Mar. 6, 1917 1,935,076 Burns Nov. 14, 1933 2,163,681 Hansen June 27, 1939 2,185,568 Ratner Jan. 2, 1940 2,197,212 Hagemeyer Apr. 16, 1940 2,221,794 Gould et al. Nov, 19, 1940 2,271,979 Jones Feb. 3, 1942 2,359,674 Pollock Oct. 3, 1944 2,918,715 Rossi Dec. 29, 1959 2,965,946 Sweet et a1. Dec. 27, 1960 

1. APPARATUS FOR PRESSING DETERGENT MATEIALS INTO CAKE FORM AT HIGH SPEED WHICH COMPRISES A DIE BOX, A PAIR OF RELATIVELY MOVABLE OPPOSED COMPANION DIE MEMBERS OF SOFT, FLEXIBLE, RESILIENT, POLYMERIC SYNTHETIC ORGANIC PLSTIC, SMALLER THAN THE DIE BOX CAVITY TO ALLOW A CLEARANCE BETWEEN DIES AND DIE BOX AS THE DIES ENTER THE DIE BOX CAVITY AND HAVING PRESSING SURFACES, THE PERIPHERAL PORTIONS OF THE PRESSING SURFACES OF THE DIES BEING CAOABLE 